If I'm on the go, I'll have to take it out of the chassis while it's in my bag so I don't damage it. In that case, it's easier to have a regular USB-C card in that port, and toss a dongle in my bag instead of the expansion card.
If I'm not on the go, I'm at a desk, and I'd still rather plug in a dongle than regularly swap an expansion card.
I'm not saying you'd never want the expansion card, but it feels pretty niche.